1. Field of the Invention
This invention relates to a novel indole diterpene compound and its use as an insecticide for control of Lepidoptera and Coleoptera species.
2. Description of the Prior Art
Toxic metabolites of fungi are thought to serve as chemical defense systems for the fungi that produce them, and may also be of use in protecting the food source from consumption by other organisms [see: Wicklow, In Toxigenic Fungi--Their Toxins and Health Hazards, H. Kurata et al. (ed.), Elsevier, N.Y., pp. 78-86 (1984)]. Dowd et al. [Ser. No. 201,143] disclosed that the class of fungal metabolites known as tremorgenic mycotoxins is toxic to insect species.
Many fungi produce specially adapted morphological structures called sclerotia that are critical to the long-term survival and propagation of the species [Willets, Biol. Rev. Cambridge Philos. Soc. 46:387 (1971); Gloer et al., J. Org. Chem. 53:5457-5460 (1988); Wicklow et al., Trans. Br. Mycol. Soc. 91:433 (1988)]. The factors which permit the long-term survival of sclerotia in soil are not fully understood. Many vascular plants are known to selectively allocate metabolites to important physiological structures as chemical defenses against herbivory [Herbivores: Their Interaction with Secondary Plant Metabolites, G. Rosenthal et al. (ed.), Academic, New York, (1979)]. By analogy, it has been suggested that fungal sclerotia may have evolved chemical defenses against predation by fungivorous insects which commonly encounter sclerotia in soil [Wicklow et al., supra (1988); Wicklow et al., Can. J. Bot. 60:525 (1982)]. However, aside from the sclerotia (ergot) of Claviceps spp. (which produce the ergot alkaloids), sclerotia have not been commonly explored for the production of unique, biologically active secondary metabolites. Gloer et al. [supra] and Wicklow et al. [supra (1988)] reported the isolation of four antiinsectan aflavinine derivatives that are selectively allocated to the sclerotia of Aspergillus flavus in concentrations effective against insects that encounter sclerotia under natural conditions.